Reduced pyrroloquinoline quinone (hereinafter also referred to as “reduced PQQ”) is a substance obtained by reducing the quinone moiety of oxidized pyrroloquinoline quinone (hereinafter also referred to as “oxidized PQQ”).
It has been reported that the reduced pyrroloquinoline quinone has much higher antioxidant activity than the conventional oxidized PQQ (Non Patent Literature 1). It is presumed that the oxidized PQQ is reduced in vivo into reduced PQQ, which seems to act as active species causing proliferation of cells or a reduction in blood sugar level. For this reason, the reduced PQQ is more effective than the oxidized PQQ, and has been receiving attention as a useful component in applications to, for example, nutritional functional foods, foods for specified health uses, nutritious supplements, nutrients, beverages, feedstuffs, animal drugs, cosmetics, pharmaceuticals, therapeutic drugs, and preventive drugs.
It has been reported that the reduced PQQ is obtained by reduction of oxidized PQQ with a typical reducing agent such as sodium borohydride or sodium dithionite, reduction of oxidized PQQ with hydrogen in the presence of a platinum catalyst, or reduction of oxidized PQQ with glutathione (for example, see Non Patent Literatures 1, 2, 3, and 4).
Patent Literature 1 proposes a method of reducing PQQ with ascorbic acid.